:root {
  --ink: #101923;
  --ink-soft: #314254;
  --paper: #f4f3ec;
  --paper-deep: #e9e7dc;
  --navy: #071a2b;
  --navy-2: #0e2d45;
  --cyan: #10b7c9;
  --cyan-soft: #d8f3f3;
  --amber: #e4a93e;
  --line: #c7c9c2;
  --line-dark: #29435a;
  --white: #ffffff;
  --mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
  --sans: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background:
    linear-gradient(rgba(16, 25, 35, 0.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(16, 25, 35, 0.035) 1px, transparent 1px),
    var(--paper);
  background-size: 24px 24px;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.72;
}

img { display: block; max-width: 100%; height: auto; }

a { color: #006d7c; text-decoration-thickness: 1px; text-underline-offset: 0.18em; }
a:hover { color: #004c58; }
a:focus-visible, button:focus-visible { outline: 3px solid var(--amber); outline-offset: 3px; }

.skip-link {
  position: absolute;
  top: 8px;
  left: 8px;
  z-index: 20;
  padding: 8px 12px;
  background: var(--white);
  color: var(--ink);
  transform: translateY(-180%);
}
.skip-link:focus { transform: translateY(0); }

.site-header {
  color: var(--white);
  background:
    radial-gradient(circle at 88% -20%, rgba(16, 183, 201, 0.3), transparent 38%),
    linear-gradient(132deg, var(--navy), var(--navy-2));
  border-bottom: 4px solid var(--cyan);
}

.masthead,
.primary-nav,
.subnav,
.page-shell,
.footer-inner {
  width: min(1180px, calc(100% - 36px));
  margin-inline: auto;
}

.masthead {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 24px;
  align-items: end;
  padding: 31px 0 24px;
}

.brand {
  color: var(--white);
  font-family: var(--mono);
  font-size: clamp(1.75rem, 5vw, 3rem);
  font-weight: 750;
  letter-spacing: -0.055em;
  line-height: 1;
  text-decoration: none;
}
.brand-dot { color: var(--amber); }

.tagline {
  max-width: 520px;
  margin: 10px 0 0;
  color: #b7cbd9;
  font-family: var(--mono);
  font-size: 0.87rem;
}

.signal-mark {
  width: 150px;
  height: 40px;
  background:
    linear-gradient(90deg, transparent 0 8%, var(--cyan) 8% 10%, transparent 10% 22%, var(--cyan) 22% 24%, transparent 24% 38%, var(--cyan) 38% 40%, transparent 40% 54%, var(--cyan) 54% 56%, transparent 56% 70%, var(--amber) 70% 72%, transparent 72% 86%, var(--amber) 86% 88%, transparent 88%);
  clip-path: polygon(0 67%, 8% 67%, 8% 25%, 24% 25%, 24% 72%, 40% 72%, 40% 40%, 56% 40%, 56% 75%, 72% 75%, 72% 18%, 88% 18%, 88% 60%, 100% 60%, 100% 66%, 82% 66%, 82% 24%, 78% 24%, 78% 82%, 50% 82%, 50% 46%, 46% 46%, 46% 78%, 18% 78%, 18% 31%, 14% 31%, 14% 73%, 0 73%);
  opacity: 0.9;
}

.primary-nav {
  display: flex;
  gap: 1px;
  align-items: stretch;
  overflow-x: auto;
  border-inline: 1px solid rgba(255,255,255,0.15);
}

.primary-nav a {
  flex: 0 0 auto;
  padding: 11px 15px;
  border-right: 1px solid rgba(255,255,255,0.15);
  color: #dbe8ef;
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.02em;
  text-decoration: none;
}
.primary-nav a:hover,
.primary-nav a[aria-current="page"] { background: var(--cyan); color: var(--navy); }

.subnav-wrap { background: #dce2e1; border-bottom: 1px solid #bac7c8; }
.subnav {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 22px;
  padding-block: 9px;
}
.subnav a {
  color: #294252;
  font-family: var(--mono);
  font-size: 0.73rem;
  text-decoration: none;
}
.subnav a:hover { color: #006d7c; text-decoration: underline; }

.page-shell { padding: 54px 0 72px; }
.article-grid {
  display: grid;
  grid-template-columns: minmax(0, 790px) minmax(220px, 1fr);
  gap: 56px;
  align-items: start;
}

.eyebrow {
  margin: 0 0 10px;
  color: #006d7c;
  font-family: var(--mono);
  font-size: 0.74rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

h1, h2, h3 { line-height: 1.18; text-wrap: balance; }
h1 {
  max-width: 820px;
  margin: 0 0 20px;
  font-size: clamp(2.35rem, 6vw, 4.9rem);
  letter-spacing: -0.055em;
}
h2 {
  margin: 48px 0 14px;
  padding-top: 13px;
  border-top: 1px solid var(--line);
  font-size: clamp(1.45rem, 3vw, 2.2rem);
  letter-spacing: -0.025em;
}
h3 { margin: 30px 0 8px; font-size: 1.12rem; }

.lede { max-width: 760px; color: var(--ink-soft); font-size: 1.18rem; line-height: 1.65; }
.article-body p { max-width: 74ch; }
.article-body li + li { margin-top: 8px; }

.hero-figure {
  margin: 36px 0 44px;
  border: 1px solid var(--line-dark);
  background: var(--navy);
  box-shadow: 10px 10px 0 rgba(6, 28, 45, 0.11);
}
.hero-figure img { width: 100%; aspect-ratio: 3 / 2; object-fit: cover; }
.hero-figure figcaption {
  padding: 10px 14px;
  border-top: 1px solid var(--line-dark);
  color: #bfd2dc;
  font-family: var(--mono);
  font-size: 0.72rem;
}

.side-rail {
  position: sticky;
  top: 24px;
  border-top: 5px solid var(--amber);
  background: rgba(255, 255, 255, 0.62);
  box-shadow: 0 0 0 1px var(--line);
  padding: 20px;
}
.side-rail h2 {
  margin: 0 0 12px;
  padding: 0;
  border: 0;
  font-family: var(--mono);
  font-size: 0.82rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.side-rail ul { margin: 0; padding: 0; list-style: none; }
.side-rail li + li { border-top: 1px solid var(--line); }
.side-rail a { display: block; padding: 9px 0; font-size: 0.88rem; text-decoration: none; }

.callout,
.era-card,
.concept-card,
.source-card {
  border: 1px solid var(--line);
  background: rgba(255,255,255,0.7);
}
.callout { margin: 30px 0; padding: 22px 24px; border-left: 5px solid var(--cyan); }
.callout strong:first-child { font-family: var(--mono); color: #006d7c; }

.era-grid,
.concept-grid,
.source-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin-block: 24px 36px;
}
.era-card,
.concept-card,
.source-card { padding: 20px; }
.era-card h3,
.concept-card h3,
.source-card h3 { margin-top: 0; }

.tool-ledger,
.reading-list,
.paper-list { margin: 26px 0; border-top: 1px solid var(--ink); }
.tool-row,
.book-row,
.paper-row {
  display: grid;
  grid-template-columns: minmax(150px, 0.8fr) minmax(0, 2fr);
  gap: 22px;
  padding: 18px 0;
  border-bottom: 1px solid var(--line);
}
.tool-row h3,
.book-row h3,
.paper-row h3 { margin: 0; font-family: var(--mono); font-size: 0.93rem; }
.tool-row p,
.book-row p,
.paper-row p { margin: 0; }

pre {
  max-width: 100%;
  overflow-x: auto;
  padding: 20px;
  border-left: 5px solid var(--cyan);
  background: var(--navy);
  color: #d9f7f8;
  font: 0.9rem/1.6 var(--mono);
}
code, kbd { font-family: var(--mono); }
kbd { padding: 2px 6px; border: 1px solid #89949b; border-bottom-width: 2px; background: #fff; }

.source-list { padding-left: 1.2rem; }
.source-list a::after { content: " ↗"; font-size: 0.8em; }
.microcopy { color: #526270; font-family: var(--mono); font-size: 0.77rem; }

.site-footer { background: var(--navy); color: #b7c9d4; border-top: 4px solid var(--amber); }
.footer-inner { padding: 38px 0 46px; }
.footer-grid { display: grid; grid-template-columns: 1fr 2fr; gap: 40px; }
.footer-brand { color: var(--white); font-family: var(--mono); font-weight: 700; }
.disclaimer {
  margin: 0;
  padding-left: 18px;
  border-left: 3px solid var(--cyan);
  font-size: 0.83rem;
  line-height: 1.58;
}
.copyright { margin: 22px 0 0; color: #78909e; font-family: var(--mono); font-size: 0.72rem; }

.error-page { min-height: 52vh; display: grid; place-items: center; text-align: center; }
.error-code { color: var(--cyan); font: 700 clamp(4rem, 15vw, 9rem)/1 var(--mono); }
.button-link {
  display: inline-block;
  padding: 10px 14px;
  border: 1px solid var(--navy);
  background: var(--navy);
  color: var(--white);
  font-family: var(--mono);
  font-size: 0.8rem;
  text-decoration: none;
}
.button-link:hover { background: var(--cyan); color: var(--navy); }

@media (max-width: 860px) {
  .masthead { grid-template-columns: 1fr; }
  .signal-mark { display: none; }
  .article-grid { grid-template-columns: 1fr; }
  .side-rail { position: static; }
  .footer-grid { grid-template-columns: 1fr; }
}

@media (max-width: 620px) {
  body { font-size: 16px; }
  .masthead, .primary-nav, .subnav, .page-shell, .footer-inner { width: min(100% - 24px, 1180px); }
  .page-shell { padding-top: 36px; }
  .era-grid, .concept-grid, .source-grid { grid-template-columns: 1fr; }
  .tool-row, .book-row, .paper-row { grid-template-columns: 1fr; gap: 6px; }
  h1 { font-size: clamp(2.2rem, 14vw, 3.45rem); }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}